Abstract
A survey was made of the concentrations of Ag, od,
Cr, Cu, Mn, and Zn found in the sand crab, Emerita analoga,
and the sand it inhabits from various points in the Monterey
Bay area of California. Geographical differences in concen¬
trations were documented and correlations between these con¬
centration patterns and possible point sources of contaminant
input associated with domestic, industrial, and agricultural
effluents were drawn. In addition, the effect of local current
patterns in the concentration of various heavy metal pollutants
was suggested by the research.
The results suggest that Emerita may be a useful bio¬
geographical marker of trace metal levels in the sandy beach
environment.
1/0
Introduction
Much work has been done since the early nineteenth
century to establish trace metal concentrations in a variety
of biological systems, including marine organisms. For
example, J. F. John in 1814 demonstrated the presence of
manganese in the carapace of the marine crustacean Potamobius
fluviatilis. Within the last ten years, with the advent of
atomic absorption spectroscopy, much more rapid and relatively
more accurate investigation has been made possible. Most of
the work to date has been concerned with the establishment of
normal trace metal concentration levels within certain species
and is cited in Goldberg's 1967 review of the literature.
The goal of the work reported herein has been first
to catalog the concentrations of certain trace metals normally
occurring within the marine anamuran crustacean, Emerita
analoga, and second to attempt to analyze for differences
in metal concentrations possibly attributable to known point
sources of contamination. Therefore, a biogeographical survey
was accomplished with special note made of local contamination
inputs.
The Monterey Bay area was chosen for study, since it
has a large number of possible trace metal inputs: 6 direct
sewage outfalls (of primary or secondary treatment only); 6
rivers and sloughs, 3 of which traverse large agricultural
areas, and at least 2 of which are used for sewage disposal;
3 major fishing and boating centers; and 2 relatively large
urban areas, Santa Cruz and Monterey.
119
The metals chosen for study were silver, cadmium,
zinc, copper, manganese, and chromium. According to Bowen
(1966), all have either high or very high potential for
pollution. These metals are currently being introduced into
the environment at a rate exceeding their annual cycling out
of the marine environment. Furthermore, all, with the ex¬
ception of copper, are highly toxic at relatively low con¬
centrations. Thus a geographic survey of the concentrations
of these metals in a given species would seem to be of value
both in terms of assessing the possible biological impact of
point sources of contamination, and also in providing base¬
line data for an area expected to receive even higher inputs
of trace metals in the future.
The sand crab, Emerita analoga (Arthropoda, amomura)
was chosen primarily because of its ubiquity in the sandy
beaches which make up a major portion of the Monterey Bay
coastline. Furthermore, these animals do not move great
distances laterally (MacGinitie, 1938) and are thus potenti¬
ally good biological markers of local conditions. The study
was limited to females only as they are very much larger,
easier to collect, and may be individually analyzed for trace
metal content.
2C
Methods and Materials
Collection
The collection of Emerita from Monterey Bay was ac¬
complished during a five day period in late April 1971. The
aim was to collect all of the organisms over as short a time
span as possible to eliminate climatic and seasonal effects.
Twenty three stations from Carmel to Santa Cruz were sampled
(Fig. 1). Approximately 20 female Emerita analoga were taken
from each beach station. While in the field, the eggs were
separated from the ovigerous females and stored in separate
acid-cleaned containers. Sediment samples from the surface
of the sand were also taken from each of the twenty three
stations. The samples of whole animals, eggs, and sediments
were then frozen and stored until further use. In late May
another set of Emerita were collected from Pt. Sur, and area
believed to be relatively unpolluted, for comparison with the
established base line of metal concentrations in the Emerita
populations from around the Monterey Bay area.
Whole Animal Procedure
For each analysis, 5 to 8 animals per station were
thawed, blotted dry, and a fresh, wet weight was recorded.
The specimens were then dried at 80°C. for approximately 24
hours. A dry weight was recorded and each of the animals
was then crushed into a fine powder, using a mortar and
pestle (Thiers, 1957). Approximately 1/2 gram of this crushed
material was digested using a modification of the Middleton¬
(
Stuckey wet digestion method (Christian and Feldman, 1970)
suggested by Martin (personal communication). In this pro¬
cedure, 5 to 7 ml of 90% nitric acid is added to the crushed
material. This suspension is refluxed for approximately two
hours, allowed to evaporate to 2 ml, and then cooled. Approxi¬
mately 5 ml hydrogen peroxide is then added and the suspension
again heated, refluxed, boiled down and diluted to 25 ml with
distilled water. This was a most successful method for the
removal of the residual organic material in Emerita. Charring
was deemed both unnecessary and undesirable in light of pos¬
sible loss of volatile elements. There were noticeable amounts
of sand-like particles remaining, but these were assumed to
be unavoidable, recognizing the habitat and feeding patterns
of Emerita, and were merely allowed to settle out of suspen¬
sion. A blank solution was run under the same conditions to
account for any contamination of reagents and vessels. The
solutions were then analyzed by atomic absorption spectro¬
scopy for the trace metals listed above, using a Perkin-Elmer
model 303 Spectrophotometer (Kahn, 1968). The effect of
light scatter on the analyses of Cd and Zn was corrected for
by reading the absorption of each of the samples (2203 A°
and adding this value to the absorption recorded for the
blank run for each particular set. Data were calculated on
the basis of ug/gram, or parts per million, dry weight
(Christian and Feldman, 1970).
ad
Eggs
Eggs were collected from the majority of the stations
sampled. The eggs collected were all under Stage 5 of de¬
velopment (Eickstadt, 1969). These were dried for 24 hours
at 80°C., and then weighed. The dried eggs were then sub¬
jected to basically the same wet digestion and atomic absorp¬
tion techniques outlined above for the whole animals with one
exception. Eggs had a higher proportional amount of lipid
per dry weight than whole animals. Consequently, several
extra steps of refluxing with both nitric acid and hydrogen
peroxide were needed. A blank was run concurrently to correct
for contamination by reagents and vessels. Only one analysis
could be made per station as a result of the very small dry
weight of eggs available. Thus there was no possibility for
statistical validation of the results obtained.
Sediments
Five sediment analyses were made per station; each
sample an aliquot of a test tube of sand collected at the
sand surface at each station. The wet digestion and atomic
absorption techniques described above were followed throughout.
The alternative of breaking down the sand granules themselves,
using hydrofluoric acid was rejected on both practical and
theoretical grounds. The crabs cannot be thought to be af¬
fected by the components of sand granules, nor can we expect
that the trace metal concentrations in these components are
substantially altered by trace metal contamination.
Results and Discussion
The results have been expressed as ppm dry weight.
This was thought to be a more reliable figure than ppm wet
weight, as the variance of the water content per sample was
considerable. Based upon weight ratios, the ppm dry may
generally be converted to ppm wet weight using the wet to dry
ratio of 3.85 for animals and 1.26 for sediment. Wet weight
figures for the eggs were not obtained.
For each metal, the mean value in ppm for whole ani¬
mals and for sediments from each individual station was com¬
pared with that of every other station using the "student t"
test. On the basis of this data, signficantly differing
populations, based on statistically different concentration
levels, were recognized and cataloged. These differences are
displayed in Figure 2, a-f, through the use of different
hashing marks on the maps of the coastline of the Bay. Note
also that the mean values and standard deviations are re¬
corded to the left of each diagram.
The results obtained for concentrations found along
the coast will be discussed according to metal.
Silver (Fig. 2a) has been documented as occuring in
marine organisms at levels ranging from 3 to 11 ppm (Vinogradov,
1953), but Bowen (1966) lists no silver values as having been
recorded for crustacea. The data reported herein lies in the
range reported by Vinogradov showing a range of 1.4 to 4.2
ppm. According to Christian and Feldman (1970), silver is
an environmental contaminant and a cumulative poison, inhibiting
24
enzymes in two ways. First, it competes with copper for
position in certain metalloenzymes, and second, it reacts
with thiol groups near enzymatic active sites, as does mercury.
Harvey (1968) asserts that the major input of silver into
biological systems is through adsorption, stating that silver
is not present as a salt in seawater. Thus adsorption and
food chain amplification may occur, and Emerita, found low on
the food chain (eating mostly plankton -- Efford, 1967) may
thus be expected to have relatively low values for this metal.
Referring to Figure 2a, we see the highest silver
content occurs at the southwestern tip of the Monterey
Peninsula. Peters (1971) in her study of metal concentra¬
tions in Pagurus samuelis also noted the highest silver con¬
centrations in this anomuran to be in populations from the
Monterey Peninsula, specifically from the area adjacent to
the Pacific Grove sewer outfall. According to Vieth (1971)
however, silver concentrations in the sewage effluent of
Pacific Grove are relatively low as compared with those values
found in the Monterey sewage effluent (under 5 ppm as compared
to 25 ppm). The high values represented at this area in
Emerita may be illustrative of current patterns which could
bring plankton from a relatively more contaminated area for
feeding or may merely represent some as yet unknown source of
input. Note however that the second most highly concentrated
area for silver was from the area near the Monterey sewer
effluent. The high levels seen in animals from the northern
tip of Monterey Bay near Santa Cruz remains unexplained.
125
Cadmium has been found in marine organisms at levels
from .15 to 3 ppm (Mullin and Riley, 1956). Again, no crus¬
tacean data is presented by Bowen (1970) for this element,
but Brooks and Rumsby (1965) report finding cadmium in the
proteins of certain molluscs. It has been found to be a
cumulative poison (Vinogradov, 1953) and Christian and Feldman
(1970) report that cadmium does inhibit certain enzymes. It
has been recorded occurring least in calcarious tissue of exo¬
skeleton, perhaps indicating that adsorption is not the major
factor in cadmium uptake. Figure 2b shows that the cadmium
concentrations found in Emerita fall in the range already
reported for marine organisms. Cadmium values were the highest
in the central Monterey Bay area, perhaps indicative of con¬
tamination from the Moss Landing or Salinas River area.
Tolan (1971) documented possible biological contamination
here in his finding of increased cadmium values in molluscs
and crustacean found in the Moss Landing area. It is interest¬
ing to note the higher values occur in the central area of
the Bay, an area more highly influenced by river and agri¬
cultural inputs and removed from the urban industrial and
domestic sewage outfalls.
Chromium is an essential element at trace levels.
It has been found to activate the enzyme phosphoglucomutase
(Strickland, 1949). However it is highly toxic at higher
levels. Bowen reports that Cr-IV is very much more toxic
than Cr-III, perhaps even carcinogenic. Chromium has been
documented in marine animals and occurs at concentrations of
126
from .2 to 1 ppm (Bowen, 1970); Fukai and Fukai and Broquet
(Goldberg, 1967) documented chromium concentrations in
Eriphia verrucosa and Pisa nodipus, two crustacean of 1.1
and .48 ppm respectively. In Figure 2c it can be seen that
in only one location did my data correspond within one order
of magnitude to these figures. Error due to contamination of
vessels and reagents was at a minimum and corrections were
made by means of a blank, therefore, confidence may be placed
in this data. The high figures of 40 to 50 ppm found in the
Monterey Basin may be illustrative of pollution due to chro¬
mium boat paint used in the harbor, domestic sewage, or in¬
dustrial input into the Bay which congregates in the basin
to the southeast around the city of Monterey. The relatively
high levels found around the Asilomar-Pt. Pinos area may re¬
inforce the earlier contention that local current systems may
move pollutant from the basin around the point. In light of
the fact that Emerita from the southern tip of the Peninsula
were uncontaminated, these higher values probably represent
contamination from the Pacific Grove sewage effluent.
Copper is found in all animals. It is a component
of metalloenzymes: many having an oxidative role. It is
also a component of heamocyanin, the crustacean blood pigment.
It is, however, according to Bowen (1970), highly toxic at
relatively low levels. Major pollution sources are mining
operations, copper piping and fungicides in soil runoffs.
Levels reported by Vinogradov (1953) in marine animals ranger
/
from 4-50 ppm; Culkino and Riley (Goldberg, 1967) cite a
value of 35.0 ppm in whole animal Cancer pagurus, another
decapod. The Emerita base line data (Fig. 2d) for copper,
reported here, is not higher than recorded elsewhere. It
is interesting to note the extremely high values recorded
at the Seaside and Fort Ord sewers which correlate directly
with Vieth's findings of high copper concentrations in the
actual effluents of the Seaside and Monterey sewage plants.
Noting the high values in the northern pocket of the
Bay, one is tempted to associate these increased copper
values with urban marine contamination taking place from the
major population centers at the north and south ends of the
Bay. Again we see relatively high values on the Monterey
Peninsula; perhaps indicative of either local current struc¬
ture or sewage contamination from Pacific Grove.
Man ganese is an essential element to physiological
functions. It has been found to be an enzyme activator for
many of the enzymes in the Krebs Cycle. It is also a con¬
stituent of many metalloenzymes found in the blood. It
competes with magnesium for position in certain other metal¬
loenzymes and thus, in higher concentrations, is an enzyme
inhibitor. Levels reported in the literature for marine
animals range from 1 to 60 ppm. The data presented in Figure
2 fall in this same range. Noting the lower solubility of
manganese in salt water over fresh water, it is interesting
to see that the highest Mn values found in Emerita were found
at each of the river inputs to the Bay. Manganese has been
28
reported to be found in very high concentrations in calcareous
tissues. In view of this, and noting the wide standard devia¬
tions exhibited, one may suspect that the molt state of the
animal may be a factor in the manganese concentrations. No
correlations with molt state of Emerita were performed.
Zinc is an element found in all organisms. It is a
component of many metalloenzymes and proteins, toxic at higher
levels in the environment. It has been found in marine or¬
ganisms at concentrations from 6 to 1500 ppm. Hiyama (Goldberg,
1967) found crustacea to have a concentration factor of well
over 500, indicating the zinc concentration in crustacea
should be over 5 ppm. The values reported herein ranged from
44 to 87 ppm. Not much deviation is seen in zinc concentra¬
tions. However, statistically differing concentration levels
were easily recognized; the highest concentrations being
found in Carmel Bay for which no explanation is drawn.
Noting that metals may act in a synergistic fashion
in either inhibition or activation of enzyme systems (Bowen,
1970), the relative concentration levels of metals were
plotted against each other for the area (Fig. 3). Actual
ppm figures are not comparable between the metals, but note
the relative levels found in the animals at the various lo¬
cations. The heights of the bars and the distinct hashing
types refer to the statistically differing ppm levels ex¬
pressed in Figure 2 for each metal.
Also in this diagram are recorded the levels found
in Emerita from Pt. Sur. for silver, manganese, chromium and
zinc, the concentrations corresponded with the concentrations
in populations having relatively lower amounts of these metals.
However for copper, and more strikingly, in the case of cad¬
mium the values found at Pt. Sur are relatively high. The
extent to which this may be illustrative of natural variability,
contrary to contamination due to pollution factors, such as
a nearby naval facility, is unknown.
Figure 4 represents a geographical comparison of
metals found in the sediments along the coastline. Silver
and cadmium were not found in any of the sediments at a value
above the detection limit of the spectrophotometer. No sta¬
tistical correlation could be found between metals. However,
in scanning the data one may perceive a general correlation.
All four metals seem to concentrate in the Monterey basin
area (Stations 4 and 5). Also, the Salinas and Pajaro River
areas (Stations 10 and 15) seem to be areas of concentrations.
The hypothesis in this work has been that sand is very much
more transient than the animals studied. The values recorded
for metal concentrations in sediment may be illustrative then
of current patterns and sand shifting. Metal concentration
may be an effective means of cataloging sediment translocation.
By plotting dry weight against ppm found per animal,
no positive or negative correlation could be found with any
of the metals.
Several problems exist in expressing the egg data:
eggs were not found at all of the stations, there was much
30
lipid still undigested after several refluxing steps, there
was no chance for statistical validation of differences, and
finally, the dry weight for the aliquot used was so small
that my ppm calculations would be subject to a great degree
of error. However, mean values for each of the Bay area egg
samples are listed below:
Standard deviation
Mean
Cd
no detectable amounts
.89
.38
Ng
8.82
37.73
Zn
5.9
8.5
Mn
2.63
5.1
18.39
Cr
8.87
13
Acknowledgements
I would like to gratefully acknowledge the invaluable
assistance and advice given me by Dr. John Martin and Dr.
Welton Lee. Thanks is extended to Dr. John Phillips for his
help in statistical analysis.
Literature Cited
Bowen, H. J. M. (1966). Trace Elements in Biochemistry.
Academic Press, London. 241 pp.
Brooks, R. R. and Rumsby, M. G. (1965). Limnol. Oceanogr.
10: 521-528.
Christian, G. D., and Feldman, F. J. (1970). Atomic Absorp¬
tion Spectroscopy. Applications in Agriculture,
Biology and Medicine. John Wiley and Sons, N.Y.
490 pp.
Efford, I. (1967). Feeding in the sand crab Emerita analoga.
Crustaceana 10(2): 167-182.
Eickstadt, L. L. (1969). The reproductive biology of the
sand crab Emerita analoga. Doctoral dissertation,
Hopkins Marine Station of Stanford University.
Goldberg, E. D. (1967). Review of Trace Element Concentra¬
tions in Marine Organisms. Puerto Rico Nuclear Center.
535 pp.
Harvey, H. W. (1968). Biological Oceanography. in Recent
Marine Sediments, a symposium. P.D. Trask, ed. Dover
Publications. N.Y. 736pp.
Kahn, Herbert (1968). Principles and Practice of Atomic
Absorption Spectroscopy. in Trace Inorganics in
Water, A symposium sponsored by the Amer. Chem. Soc.,
Washington, D.C. 396 pp.
MacGinitie, G. E. (1938). Movements and Mating habits of
the sand crabs, Emerita analoga. Amer. Midl. Natl.
19: 471-481.
/3.
Mullin, J. B. and Riley, J. P. (1956). The occurrence of
cadmium in seawater and in marine organisms and
sediments. J. Mar. Res. 15: 103-115.
Peters, J. (1971). Trace Metals in the marine intertidal
hermit crab, Pagurus samuelis in California waters.
On file Hopkins Marine Station, Pacific Grove.
Strickland, L. H. (1949). The activation of phosphogluco¬
mutase by metal ions. Biochem. J. 44: 190-198.
Thiers, R. E. (1957). Contamination in trace element analysis
and its control. in Methods of Biochemical Analysis.
V.5. D. Glick, ed., Interscience, N.Y. 502 pp.
Tolan, T. (1971). Trace metals in common marine foods. On
file at Hopkins Marine Station, Pacific Grove.
Vieth, R. (1971). Trace metals in Monterey Peninsula sewerage.
On file at Hopkins Marine Station, Pacific Grove.
Vinogradov, A. P. (1953). The Elemental Chemical Composition
of Marine Organisms. Sears Foundation for Marine
Research, New Haven. 535 pp.
3
C
O
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FIGURE 1.
of the Monterey Bay Area showing collection
sites.
13.
23
Santa
Cruz
+ 20
2221
8
3

24
Monterey

Carmel
CarmelR.
17
136
Watsonville
16
15

Moss Land
12
17
10
SalinasRive
8
Sewer
Outfalls
6 Monterey
7 Seaside
8 FtOrd
9 Marina
C
FIGURE 2a. Silver concentrations found in Emerita from the
Monterey Bay area.
Mean values and standard deviations for
each station are shown at left.
Significantly differing populations are
indicated by distinct hash marks noted along
the coastline.
yearly aupploments and weekly Notices to
not to tow submerged objects across the transit lane
Mariners. Copies of the regulations may
when it is in use.
+045
be obtained at the office of the District
Engineer, Corps of Engineers in San Fran¬
Soquel
cisco, Calif.
P
OTAN
Anchorage Regulations may be obtained



Cappo
at the office of the Commander, 12th Coast
g



Guard District in San Francisco, Calif.
ereg


Refer to section numbers shown with


0
area designation.

Watsonville
.
PRedsandHil
PR. TRS.
VOON 1460 k42)
SILVER
-2.5 ppm


57



hor
2.5 -2.75

o wo
oss Landing Karber
Lag.
O
2.76-4.0
nvnille
4. - 5
aro sohnes
OIR. TR
r
EE
S
Rot W&c

.
a  20
S

MONTER
Veande
Monte
Monterey Peninsula


Rot WaG

A

.

22 oma a
Va.


Carmel

138
1
C
FIGURE 2b. Cadmium concentrations in Emerita from the
Monterey Bay area.
Mean values and standard deviations for
each station are shown at left.
Significantly differing populations are
indicated by distinct hash marks noted along
the coastline.
C
vearly supplements and weekly Notices
not to tow submerged objects across the transit lane
Mariners. Copies of the regulations may
when it is in use.
+045
be obtained at the office of the District
Engineer, Corps of Engineers in San Fran¬
Squl
cisco, Calif.

aor
Anchorage Regulations may be obtained
T
OTANK


at the office of the Commander, 12th Coast
pg
Son
es
Guard District in San Francisco. Calif.

1

Refer to section numbers shown with



area designation.


eonalle
RRedsandHil

R. TRS.
KOON 146662).
CADMIUM
-2.5ppm



KS(S OF TWO)
2.51 - 3.0
Moss Landing Herber
o.. Lag.
O

.
3.0 -3.52
ano ones
(IDD 630 KH2)

AERO
Rot W & G

dei
Se
A
MONTENE
enode

Del Monte
Monterey Peninsula


Rera



Loma in


larmel
S
TOWERCMELTE OT

040

140
0
FIGURE 2c. Chromium concentration found in Emerita from the
Monterey Bay area.
Mean values and standard deviations for
each station are shown at left.
Significantly differing populations are
indicated by distinct hashmarks noted along the
coastline.
yearly supplements and weekly Notie
not to tow submerged objocts across the transit lane
Mariners. .Copies of the regulations may
when it is in use
+015
be obtained at the office of the District
Engineer, Corps of Engineers in San Fran¬
Soquel
cisco. Calif.

OTANK
Anchorage Regulations may be obtained

Capog

at the office of the Commander, 12th Coast



ranay L
cnr.
Guard District in San Francisco, Calif.
CRUZ
PLakes
Ver

Reter to section numbers shown with


n

area designation.

Watsonville
RrdsandHl
a
CHROMIUM
0-
ppm
2


S
3-30
STACKS(S OF TWO

oss Landing Karber
Mo. Lag.
OTRR
7
31-40
tville

41-53
o e
O r.
(KIDD63O KH2)
Marina
AERC
Rot wamc

n0 120

o
Kn.

Del Monte
Montorey Peninsula


Rot W & G


.
22 Laa
S

Carmel
.

oregeneter vongren,

040

5TOHE N0.
e
O
FIGURE 2d. Copper concentrations found in Emerita from the
Monterey Bay area.
Mean values and standard deviations for
each station are shown at left.
Significantly differing populations are
indicated by distinct hash marks noted along
the coastline.
yearly supplements and wookly Notices to
not to tow submerged objects across the transit lane
Mariners. Copies of the regulations may
when it is in use
+045
be obtained at the office of the District
Engineer, Corps of Engineers in San Fran¬
Squel
cisco, Calif.
g
Anchorage Regulations may be obtained
OTANI
Coaa
at the office of the Commander, 12th Coast
Aptor

ara
Guard District in San Francisco, Calif.
en
Reier to section numbers shown with

area designation.

snvile
ORed Sand Hill
R. TRS
AKPON 14602)
COPPER
40-60 ppm

o


Eehons
ACKS(S O
61-70
oss Landing Harber
Moss Lag.
OTAR

71-90
e

91-110
ooen
O/R. TR
(KIDD630 KH2)
PNarn.
AERO
Rot W& G


re



endde

Del Monte
Monterey Peninsula

230


Rot Wap;G

2 .
2 loma





ONEEICANNEUTE NONASTERN
1
600

STONE HO.
6
j
O
FIGURE 2e.
Manganese concentrations in Emerita found in the
Monterey Bay area.
Mean values and standard deviations for
each station are shown at left.
Significantly differing populations are
indicated by distinct hash marks noted along
the coastline.
or





vearly supplements and woekly Notices to
not to tow submerged objects across the transit lane
Mariners. Copies of the regulations may
when it is in use
be obtained at the office of the District
1015
Engineer, Corps of Engineers in San Fran¬
Squel +
cisco, Calif.
Anchorage Regulations may be obtained
OTAN


C
at the office of the Commander, 12th Coast
Pgs.
Ptan
Guard District in San Francisco, Calif.

Grdat
eeg
Refer to section numbers shown with

area designation.
d
.
Watsonville
RedSand
(OON 1460R2)
MANGANESE
I1-20ppm
21

45
DSTACKS(S OF TWO
2

Moss Landing Harber
Moss Lag.
OTANK

71
46
i-
Saso ohes
Je. r.
KIDD63O KHD
Marina
AERC
Rot W & (







essde

Monterey Peninsula
Del Monte


Rot W & G

SIACK
ona h.
Dan.


i care


TONERCANELITE NONASTERN)
200

STONE NO.
146
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FIGURE 2f. Zinc concentrations found in Emerita from the
Monterey Bay area.
Mean values and standard deviations for
each station are shown at left.
Significantly differing populations are
indicated by distinct hash marks noted along
the coastline.
yearly suppléments and weekly Notices to
not to tow submerged objects across the transit lane
Mariners. Copies of the regulations may
when it is in use.
+015
be obtained at the office of the District
Engineer, Corps of Engineers in San Fran¬
Squel
)
cisco. Calif.

ajors

TANK
Anchorage Regulations may be obtained


C
a
A
at the office of the Commander, 12th Coast

.
Guard District in San Francisco, Calif.


Refer to section numbers shown with

area designation.


.
Watsonville
Red Sand Hill
R. 7RS.
KOON 1460 KH2)
TINC
40-50 ppm


2.

51-70
STACKS(S OF TWO
Moss Landing Harber
o 14
OTAN

.
71-80
89
81
SANO GUNALR
Oe. 72
630 K2)
AM
ER
Rot W&C

240 k
MONTERE

.

Dyl Monte
Monterey Peninsula


Rot W & G

n
Loma ai


Carmel

QOVERICMRNELITE MONASTERN)

o0


116
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FIGURE 3. Relative concentrations of metals found in Emerita,
Stationn
ber.
Distinct hashing
organi
types refer to significantly differing populations.
O


=

ce
150
0
FIGURE 4. Relative concentrations of metals found in
sediments, organized by Station number, with
corresponding absolute values listed beneath.
O
(OO
O
00
O
NO
C
—
C
C

O
O
O
O
3

0
O
N


5